Method to add value to mysql: Use the "INSERT INTO" statement to insert one or more rows of data into an existing table in the database; the syntax format is "INSERT INTO table name [column name 1 [, ... column name n] ] VALUES (value 1) [… , (value n)];”.
After the database and table are successfully created, you need to add the database table Insert data into . In MySQL, you can use the INSERT INTO statement to insert one or more rows of tuple data into an existing table in the database.
: Specify the name of the table to be operated on.
: Specify the column name into which data needs to be inserted. If data is inserted into all columns in the table, all column names can be omitted, and INSERT
VALUES(…) can be used directly.
VALUES or VALUE clause: This clause contains the list of data to be inserted. The order of data in the data list should correspond to the order of columns.
In MySQL, processing multiple inserts with a single INSERT statement is faster than using multiple INSERT statements.
When using a single INSERT statement to insert multiple rows of data, you only need to enclose each row of data in parentheses.
Add values to all fields in the table
There are two ways to insert values into all fields in the table: one is to specify all field names; the other It does not specify the field name at all.
[Example 1] Insert a new record in the tb_courses table, the course_id value is 1, the course_name value is "Network", the course_grade value is 3, and the info value is "Computer Network".
Before performing the insert operation, view the SQL statement and execution results of the tb_courses table as follows.
mysql> SELECT * FROM tb_courses;
Empty set (0.00 sec)
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The query result shows that the current table content is empty and there is no data. Next, perform the operation of inserting data. The input SQL statement and execution process are as follows.
You can see that the record was inserted successfully. When inserting data, all fields of the tb_courses table are specified, so new values will be inserted for each field.
The order of the column names after the INSERT statement does not need to be the order when the tb_courses table is defined. That is, when inserting data, it is not necessary to insert in the order defined by the table, as long as the order of the values is ensured to be the same as the order of the column fields.
[Example 2] Insert a new record in the tb_courses table, the course_id value is 2, the course_name value is "Database", the course_grade value is 3, and the info value is "MySQL". The input SQL statement and execution results are shown below.
When using INSERT to insert data, the column name list column_list is allowed to be empty. At this time, the value list needs to specify a value for each field of the table, and the order of the values must be the same as the order in which the fields are defined in the data table. same.
[Example 3] Insert a new record in the tb_courses table, the course_id value is 3, the course_name value is "Java", the course_grade value is 4, and the info value is "Jave EE". The input SQL statement and execution results are shown below.
The INSERT statement does not specify an insertion list, only a value list. In this case, the value list specifies the inserted values for each field column, and the values must be in the same order as the fields are defined in the tb_courses table.
Note: Although the column name of the inserted data can be ignored when using INSERT to insert data, if the value does not contain the column name, the value after the VALUES keyword must not only be complete, but also the order must be the same as the order of the columns when the table is defined. same. If the structure of the table is modified and columns are added, deleted, or their positions are changed, these operations will cause the order in which data is inserted in this way to change at the same time. If you specify column names, they will not be affected by table structure changes.
Add values to specified fields in the table
Insert data into specified fields in the table. Insert values into only some fields in the INSERT statement, while other fields The value is the default value when the table is defined.
[Example 4] Insert a new record in the tb_courses table, the course_name value is "System", the course_grade value is 3, the course_info value is "Operating System", the input SQL statement and execution results are as follows.
mysql> INSERT INTO tb_courses
-> (course_name,course_grade,course_info)
-> VALUES('System',3,'Operation System');
Query OK, 1 rows affected (0.08 sec)
mysql> SELECT * FROM tb_courses;
+-----------+-------------+--------------+------------------+
| course_id | course_name | course_grade | course_info |
+-----------+-------------+--------------+------------------+
| 1 | Network | 3 | Computer Network |
| 2 | Database | 3 | MySQL |
| 3 | Java | 4 | Java EE |
| 4 | System | 3 | Operating System |
+-----------+-------------+--------------+------------------+
4 rows in set (0.00 sec)
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You can see that the record was inserted successfully. As the query results show, an integer value 4 is automatically added to the course_id field here. At this time, the course_id field is the primary key of the table and cannot be empty. The system automatically inserts an auto-incrementing sequence value for this field. When inserting records, if some fields do not specify an insertion value, MySQL will insert the default value when the field is defined.
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